View Full Version : Replace old thermostat without labels
blue62topaz
Dec 14, 2008, 09:58 AM
Hi. I am trying to install a new programmable thermostat from one that is not labeled. When I remove the outer cover, I see two (2) red wires, (2) black wires, one (1) white wire and one (1) tan-ish color. There is no green, yellow, blue, etc. I have replaced a few of these thermostats before, but they were all color coded. Please help me determine which wires from the older connects with the newer model wires. Thanks much! :confused:
KC13
Dec 14, 2008, 10:01 AM
Need more info. What are the terminal designations on the old t-stat? Don't disconnect anything yet...
blue62topaz
Dec 14, 2008, 10:39 AM
I don't recognize terminals or what they are. (My bad :o) All I see are wires coming through one hole from the back of the thermostat. I haven't disconnected anything yet. I attached a photo. Hopefully it is clear enough for you to recognize the connections.
hvac1000
Dec 14, 2008, 11:10 AM
What kind of system?
blue62topaz
Dec 14, 2008, 01:49 PM
It says Lenox, spelled with one 'n'.
blue62topaz
Dec 14, 2008, 01:52 PM
Oops. It IS Lennox with two 'n'.
hvac1000
Dec 14, 2008, 02:06 PM
Complete and exact model of furnace
Complete and exact model of old thermostat
Post both
blue62topaz
Dec 14, 2008, 02:35 PM
Furnace: Lennox HP18-411U-3P
T-stat: Lennox 72F1101
hvac1000
Dec 14, 2008, 02:48 PM
Furnace: Lennox HP18-411U-3P
T-stat: Lennox 72F1101
From what I can tell that unit is about a 1984 vintage heat pump. Bad news is that someone wired it with non color code wiring which you already new. I can provide you with a universal wiring change over diagram and you will have to identify every wire you remove with the terminal it came off so as to use this universal change over diagram to transpose the old designated wires to the new thermostat terminals. Other option is to sound out each wire and see exactly where it goes on the air handler to find out exactly what it is used for. The next option is to have a professional do a on site srevice call to replace the thermostat. Sorry but under these circumstances this is all I can do.
Look under lennox 16,18,19 series
blue62topaz
Dec 14, 2008, 02:57 PM
Thanks a million for your help. I will have a professional install it just for safety.
hvac1000
Dec 14, 2008, 03:03 PM
That is a smart idea. This way if they burn up the new thermostat they will have to get you a new one.